Receivers for cycle encoded signals

ABSTRACT

In some embodiments, the inventions includes a transmitter including a cycle encoding circuit to receive a data input signal and to provide a full cycle encoded signal in response thereto by continuously joining portions of different encoding signals. Some of the encoding signals have a different frequency than others of the encoding signals and some of the encoding signals have a different phase than others of the encoding signals. Data is represented in data time segments of the full cycle encoded signal and no data time segment has more than one cycle of an encoding signal. In some embodiments, a receiver receives the cycle encoded signal and recovers data of the data input signal.

RELATED APPLICATION

The present application and application Ser. No. 10/625,945 entitled“Transmitters Providing Cycle Encoded Signals” were filed on Jul. 23,2003, have identical specifications (except for titles, technical fielddescription, claims, and abstract), and claim related subject matter.

BACKGROUND OF THE INVENTION

1. Technical Field of the Inventions

The inventions relate to receivers for cycle encoded signals and torelated systems.

2. Background Art

Inter symbol interference (ISI) degrades signal integrity throughsuperimposition of pulses at varying frequencies. Data patterns withhigh frequency pulses are susceptible to ISI. Higher frequency pulsesmay phase shift more and attenuate more relative to lower frequencypulses leading to loss of the higher frequency pulses when superimposedwith lower frequency pulses. The distortion to data patterns caused byISI may lead to errors. The frequency at which uncompensated random datapatterns in conventional signaling can be transmitted may be limited byISI.

Equalization and Nyquist signaling are two solutions to ISI that havebeen proposed. Equalization is a curve-fitting solution that attempts torestore amplitude for higher frequency pulses in susceptible datapatterns. It seeks to anticipate lost data and restore it throughpre-emphasizing the amplitude on narrow pulses. Disadvantages ofequalization include that it is at best a curve fitting solution,tweaking the amplitude of higher frequency pulses in random pulses ofdata to restore any anticipated loss in amplitude. The anticipated lossis very system specific and pattern specific, thus requiring tuning forpredicted data patterns and for each custom system it is used in. It issusceptible to unpredicted data patterns and varying system transferfunctions. The iterative nature of such solutions results intime-consuming and system-specific implementations, possibly neverconverging to optimal solutions.

Nyquist signaling is another prior art solution for ISI, which uses araised cosine or sinc function pulses in the time domain to overcomeISI. The complexity to implement such functions is prohibitive inpractice.

In Manchester encoding, the signal includes discontinuities at a bitcell boundary which may lead to high ISI. Some Frequency Shift Keying(FSK) encoding schemes avoid discontinuities at bit cell boundaries butFSK takes multiple cycles to represent a 0 or 1 data value.

In source synchronous signaling, data signals and one or more associatedclock or strobe signals are sent from a transmitter to a receiver. Theclock or strobe signal is used by the receiving circuit to determinetimes to sample the data signals.

In some signaling techniques, timing information can be embedded intothe transmitted data signal and recovered through a state machine. Aninterpolator receives a number of clock or strobe signals from, forexample, a phase locked loop or a delayed locked loop. The recoveredtiming is used to select among or between the clock or strobe signalsreceived by the interpolator and provide the selected clock or strobesignal to a receiver to control sampling of the incoming data signal. Insome implementations, training information is provided in the datasignal to get the proper sample timing before actual data istransmitted. The training information can be provided from time to timeto keep the sample timing. In other implementations, traininginformation is not used, but the sample timing is created from the datasignals of prior time. There are various techniques for embedding timinginformation. The 8B/10B technique is a well known technique.

The transmission of signals may be in a multi-drop (one transmitter tomultiple receivers) or point-to-point (one transmitter to one receiver)environment. The transmission may be uni-directional, sequentialbi-direction, or simultaneous bi-directional.

Different voltage levels rather than merely just low and high have beenused to represent more values than merely just 0 and 1.

Noise on signals on conductors may cause the signals to be corrupted. Atechnique to reduce the effect of noise is to transmit the data on twowires and then reject the noise in the receiver by looking at thedifference between the received signals rather than the absolute values.Typically, one conductor carries a signal that is the inverse of theother conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventions will be understood more fully from the detaileddescription given below and from the accompanying drawings ofembodiments of the inventions which, however, should not be taken tolimit the inventions to the specific embodiments described and shown,but are for explanation and understanding only.

FIGS. 1 and 2 are each a block diagram representation of a systemaccording to some embodiments of the inventions.

FIG. 3 is a block diagram representation of a system including atransmitter and receiver in FIG. 1 according to some embodiments of theinventions.

FIG. 4 is a block diagram representation of a system including examplesof the transmitter and receiver of FIG. 3 according to some embodimentsof the inventions.

FIG. 5 is a timing diagram that shows signals according to someembodiments of the inventions.

FIG. 6 is a chart that shows signals according to some embodiments ofthe inventions.

FIG. 7 is a timing diagram for the receiver of FIG. 4 that shows signalsaccording to some embodiments of the inventions.

FIG. 8 is a block diagram representation of a synchronizing circuit thatoptionally may coupled to the receivers of FIGS. 4, 10, and 12 accordingto some embodiments of the inventions.

FIG. 9 is a block diagram representation of details of the periodicsignal deriving circuit of FIG. 8 according to some embodiments of theinventions.

FIG. 10 is a block diagram representation including an example of thereceiver of FIG. 3 according to some embodiments of the inventions.

FIG. 11 is a timing diagram for the receiving of FIG. 10 that showssignals according to some embodiments of the inventions.

FIG. 12 is a block diagram representation of a system according to someembodiments of the inventions.

FIG. 13 is a timing diagram that shows signals according to someembodiments of the inventions.

FIGS. 14 and 15 are each a block diagram representation of a systemaccording to some embodiments of the inventions.

DETAILED DESCRIPTION

A. Overview

The inventions described herein include a system having a transmitterthat encodes a data signal into a cycle encoded signal (CES). A CES ismade of portions of different periodic encoding signals which arecontinuously joined, wherein data is represented by the encoding signalsin data time segments of the cycle encoded signal. Some of the encodingsignals have a different frequency and/or phase than others of theencoding signals. In a CES, at least some of the data time segments donot include more than one cycle of a particular encoding signal. In afull CES, no data time segment has more than one cycle of an encodingsignal. In a partial CES, some data time segments have more than onecycle of an encoding signal, and other data time segments do not havemore than one cycle of an encoding signal. The CES's described inconnection with FIGS. 4, 5, 7, 10, 11, 12, and 13 are full CES's. In theCES's described in connection with FIGS. 4, 5, 7, 10, 11, 12, and 13,there is only one encoding signal per data time segment. In otherembodiments, one encoding signal may be used in part of a data timesegment, while another encoding signal may be used in the remainder ofthe data time segment.

In some embodiments, a complementary cycle encoded signal (CCES) is alsocreated. The inventions also include receivers to receive the CES, andin some embodiments the CCES, and recover the data or, in someembodiments, an inverse of it.

The use of specific frequencies (F, F/2, etc.) rather than many, perhapsrandom, low and high frequency signals can reduce or eliminate ISI. TheCES and CCES are referred to as controlled frequency signals becausethey involve a limited number of frequencies rather than a multitude offrequencies.

Referring to FIG. 1, a system 10 includes a chip or portion of a chip 14and a chip or portion of a chip 16. In the case in which 14 and 16represent portions of chips, they may be in the same chip. Transmitters20 . . . 22 represent N transmitters, conductors 24A, 24B . . . 26A, 26Brepresent N sets of two conductors, and receivers 28 . . . 30 representN receivers. Transmitters 20 . . . 22 provide CES's and CCES's onconductors 24A, 24B . . . 26A, 26B to receivers 28 . . . 30.Transmitters 40 . . . 42 represent M transmitters, conductors 44A, 44B .. . 46A, 46B represent M sets of two conductors, and receivers 48 . . .50 represent M receivers. M may be the same number as N or a differentnumber. Transmitters 40 . . . 42 provide CES and CCES on conductors 44A,44B . . . 46A, 46B to receivers 48 . . . 50. Transmitters and receiversmay be treated in groups of pairs of transmitters and receivers.

In FIG. 1, conductors 24A, 24B . . . 26A, 26B, and 44A, 44B . . . 46A,46B are shown as transmitting signals in a single direction.Alternatively, bi-directional conductors may be used. For example, inFIG. 2, a system 60 includes a chip or portion of a chip 64 and a chipor a portion of a chip 66 in which transmitter/receivers 70 . . . 72 arecoupled to transmitter/receivers 78 . . . 80 through bi-directionalconductors 74A, 74B . . . 76A, 76B. The transmission may be sequentialbi-directional or simultaneous bi-directional.

The CES may be used in connection with various encoding techniques suchas 8b/10b encoding. The data transmitted in a CES is not limited to aparticular content or meaning. Accordingly, the data of the CES mightconvey commands, addressing information, and traditional data. Two orthree of these types of content (commands, address, and traditionaldata) could be time multiplexed or packetized. Alternatively, CEScarrying these three types of content could be kept separate ondifferent conductors. It could be that one or two of these types ofcontent are conveyed through the CES, while others of the types ofcontent are conveyed through other types of signaling. It is notnecessary that the CES be used in a system that includes addressing.

Although the inventions described herein refer to transmission of datain a CES and perhaps a CCES. That does not exclude other signals thatare not a CES or CCES being passed at other times over the conductors ofFIGS. 1 and 2. For example, there could be some commands that are not aCES or CCES that pass over conductors that at other times carry a CES orCCES. Examples of other signals include the voltage being held constant;the lines being put in a high impedance mode; different voltages thanare used in CES or CCES; some lower or higher frequency signals, etc.

B. Transmitter and Receiver of FIG. 3

FIG. 3 illustrates a transmitter 102 and a receiver 104, which areexamples of transmitter 20 and receiver 28 in FIG. 1. Referring to FIG.3, a periodic reference signal source 110 provides a periodic referencesignal, such as a clock or strobe signal. Periodic signal source 110 maybe created through various circuits including a phase locked loop (PPL),a delay locked loop (DLL), and a crystal oscillator. In someembodiments, the periodic reference signal has a particular phaserelationship with the data input signal received by transmitter 102 onconductor(s) 108. The data input signal may be single ended ordifferential. In some embodiments, the periodic reference signal is inphase with the data bits of the data input signal while in otherembodiments they are not in phase. The period of the reference signalmay be the same as the time length of a data bit cell of the data inputsignal or it may be different (for example, half as great or twice asgreat) than the length of the data bit cell.

Transmitter 102 includes a cycle encoding circuit 112 and acomplementary cycle encoding circuit 114, each of which receive the datainput signal and the periodic reference signal and encode the data inputsignal into the CES and CCES. The CES and CCES are driven by drivers 122and 124 to interconnects 24A and 24B, respectively, and receiver 104.

An initial receiving circuit 134 receives the CES and CCES and providesat least one signal to delay circuit 138 in response thereto. Logiccircuit 142 determines the value of the data input signal that wasencoded as the CES and CCES in response to at least one delayed signal.The data output (data out) signal may be identical to the data inputsignal or have a known relationship to the input signal. For example,the data out signal may be in the inverse of the data input signal. Ofcourse, there are other ways in which to determine the represented valueof the CES and CCES.

C. Transmitters, Receivers, and Synchronizer Circuits of FIGS. 4-9.

1. Transmitter of FIGS. 4-6.

FIG. 4 illustrates a transmitter 150 and a receiver 180, which areexamples of transmitter 102 and receiver 104 in FIG. 3. Referring toFIG. 4, a PLL 148 provides a periodic reference signal PRSF withfrequency F, where PLL 148 is an example of periodic signal source 110in FIG. 3. The PRSF may be sinusoidal or non-sinusoidal. A cycleencoding circuit 152 and a complementary cycle encoding circuit 154 areexamples of cycle encoding circuits 112 and 114 in FIG. 3. Cycleencoding circuit 152 includes delay circuit 162, delay and invertcircuit 164, delay and divide circuit 166, and delay, divide, and invertcircuit 168, and a multiplexer (MUX) 156. Circuits 162-168 provideencoding signals SF, SF*, SF/2, and SF/2*, where SF has a frequency F;SF* has frequency F and is an inverse of SF; SF/2 has a frequency F/2,but is otherwise aligned with SF; and SF/2* is an inverse of SF/2. Inthe example, the SF has the same frequency as the PRSF signal. Encodingsignals SF, SF*, SF/2, and SF/2* are selectively passed by MUX 156 underthe control of the data input signal. Delay circuit 162 is notessential, but may be used to align SF with the other signals. Further,it is not essential that circuit 166 provide delay. To the extent delayis needed to align SF, SF*, SF/2 and SF/2* (as shown in FIG. 5), thenthe delay can be provided by circuits 162-168.

Various techniques can be used to control when MUX 156 selects one ofthe encoding signals. For example, the PRSF, the SF, or another signalcould be used to control when MUX 156 passes one of the encodingsignals.

FIG. 5 illustrates a timing diagram of the CES and encoding signals SF,SF*, SF/2, and SF/2* for data time segments 1-8 according to someembodiments. In the example of FIGS. 4-7, the data time segment is theperiod (cycle) of the PRSF from PLL 148. MUX 156 lets a different one ofthe SF, SF*, SF/2, and SF/2* signals through MUX 156 depending on thestate of the data input signal and which signal was passed through MUX156 in the previous data time segment. The signal passed by MUX 156 ineach data time segment is shown in bold. For example, in data timesegments 1 and 2, SF/2 is passed; in data time segments 3 and 4, SF ispassed; in data time segment 5, SF/2 is passed; in data time segment 6,SF* is passed; in data time segment 7, SF/2* is passed; in data timesegment 8, SF is passed.

The CES in FIG. 5 illustrates the meaning of the term “cycle” in a datatime segment. For example, in data time segments 3, 4, 6, and 8, thereis one cycle. In data time segments 1, 2, 5, and 7, there is a halfcycle, which is less than one cycle. If the SF had twice the frequencyshown in FIG. 5 and was passed by MUX 156, then there would be twocycles in a data time segment.

In the convention of FIG. 5, the CES is selected to be half thefrequency of the PRSF when the data input signal is a logical 0 and thesame frequency as the PRSF when the data input signal is a logical 1. Ofcourse, the opposite convention could have been used.

As can be seen in FIG. 5, the CES of FIGS. 4 and 5 is a full CES in thateach of encoding signals SF, SF*, SF/2, and SF/2* has a period that isequal to (SF and SF*) or greater than (SF/2 and SF/2*) the time of thedata time segments. Accordingly, no data is represented by more than onecycle of an encoding signal. Of course, though imperfections in thecircuits, a cycle could occasionally be slightly larger than a data timesegment and the CES would still be a full CES.

FIG. 6 is a chart that illustrates the next signal that could be passedby MUX 156 in some embodiments. As can be seen in FIG. 6, the choice ofencoding signal to be passed by MUX 156 is made so that there are notdiscontinuities in the signal. For example, if the previous signal wasdecreasing in voltage at the end of the previous data time segment, thechosen next signal decreases at the beginning of the next data timesegment. If the previous signal was increasing in voltage at the end ofthe previous data time segment, the chosen next signal increases at thebeginning of the next data time segment. Note that the place in anencoding signal where a cycle begins may be different than is shown inFIGS. 5 and 6.

As noted, the CES is made of continuous portions of the encoding signalsSF, SF*, SF/2 and SF/2*. However, in practice they might not beperfectly continuous because of possible imperfections in MUX 156 ordifferent delays in circuits 162-168.

Referring to FIG. 4, complementary cycle encoding circuit 154 provides aCCES which is driven by driver 124 to interconnect 24B and receiver 180.Complementary cycle encoding circuit 154 includes delay and invertcircuit 172, delay circuit 174, delay, divide and invert circuit 176,and delay and divide circuit 178 to produce signals SF*, SF, SF/2*, andSF/2, respectively, which are the inverses of SF, SF*, SF/2, and SF/2*produced by cycle encoding circuit 152.

2. Receivers of FIGS. 4-7.

In FIG. 4, receiver 180 includes initial receiving circuit 182 and delaycircuit 184, which are examples of initial receiving circuit 134 anddelay circuit 138. Exclusive-OR (XOR) gate 190, flip-flops 196 and 198,AND gate 202, and AND gate 204 are examples of logic circuit 142 in FIG.3. Of course, the circuit in FIG. 3 is not limited to the details shownin FIG. 4. Initial receiving circuit 182 may be a comparator thatcompares the difference between the CES and CCES. The received signal(RS) output by initial receiving circuit 182 is approximately a squarewave that changes from a high voltage (H) to a low voltage (L) or L to Hwhen the voltages of CES and CCES cross.

Delay circuit 184 delays RS by about ¼ of a data time segment (¼ T delaysignal) and by about ¾ of a data time segment (¾ T delay signal). Delaycircuit 184 may be made of a delay chain or DLL. Delay circuit 184 mayalso provide a delay of one data time segment to provide a 1 T delaysignal, but this is not required for all embodiments. The 1 T delaysignal may be used in the optional additional circuit such as in FIG. 8.

The outputs of delay circuit 184 are provided to XOR gate 190. Table 1below shows the truth table for XOR gate 190 and compares it to thevalue represented by CES and CCES. The input to XOR 190 is the same asthe output of delay circuit 184. As can be seen, in this particularexample, when the value represented by CES and CCES is 0, the output ofXOR gate 190 is 0; and when the value represented by CES and CCES is 1,the output of XOR gate 190 is 1. This is arbitrary and the oppositevoltages could correspond to 0 and 1.

TABLE 1 Output of Value represented ¼ T Delay ¾ T Delay XOR 190 by CESand CCES 0 0 0 0 0 1 1 1 1 0 1 1 1 1 0 0

Although the output of XOR 190 includes the correct data at data timesegment t1, t2, t3, t4, t5, and t6, additional circuits (flip-flops 196and 198, AND and AND gates 202 and 204) are used provide a data outsignal that includes the correct data between t1, t2, t3, t4, t5, t6,and t7. This can be seen in the following example of FIG. 7.

FIG. 7 shows an example of RS (output of initial receiving circuit 182),the ¼ T delay and ¾ T delay signals from delay circuit 184, the outputof XOR gate 190, the Q1 and Q2 outputs of flip-flops 196 and 198, andthe output of AND gate 202 for data time segments 1+, 2+, 3+, 4+, 5+,and 6+. Data time segments 1+-6+ correspond to data time segments 1-6 inFIG. 5 but are slightly delayed in time through driver 122, interconnect24A, and initial receiving circuit 182. FIG. 7 follows the conventionthat a “0” represents a low voltage and a “1” represents a high voltage.The opposite convention could be used. Flip-flops 196 and 198 are in thereset condition (Q1 and Q2 are both 0) at time t0.

At time t1, when RS has a falling edge, the ¼ T delay and ¾ T delay areboth 1 so XOR 190 outputs a 0. The falling edge of RS causes flip-flip198 to output as Q2 what is at its D input, which is a 0. Q1 continuesto be 0. Accordingly, the output of AND gate 202 is a 0.

At time t1.5, RS does not transition. Accordingly, Q1 and Q2 do notchange and the data out signal does not change.

At time t2, when RS has a rising edge, the ¼ T delay and ¾ T delay areboth 0 so XOR 190 outputs a 0. The rising edge of RS causes flip-flip196 to output as Q1 what is at its D input, which is a 0. Q2 continuesto be 0. Accordingly, the output of AND gate 202 is a 0.

At time t2.5, when RS has a falling edge, the ¼ T delay is 1 and the ¾ Tdelay is 0 so XOR 190 outputs a 1. The falling edge of RS causesflip-flip 198 to output as Q2 what is at its D input, which is a 1. Q1continues to be 0. Accordingly, the output of AND gate 202 continues tobe a 0 even though there was a transition of RS at time t2.5.

At time t3, when RS has a rising edge, the ¼ T delay is 0 and ¾ T delayis 1 so XOR 190 outputs a 1. The rising edge of RS causes flip-flip 196to output as Q1 what is at its D input, which is a 1. Q2 continues tobe 1. Accordingly, the Output Data from AND gate 202 changes to a 1shortly following time t3. The amount of time between the transition inRS at t3 and the change of the Output Data depends on delays betweenflip-flops 196 and 198 and AND gate 202. Note that the signals of FIG. 7are not necessarily to scale. Indeed, the delay between a change in thechange in the RS signal and the change in data out signal may besomewhat smaller than is shown in FIG. 7.

At time t3.5, when RS has a falling edge, the ¼ T delay is 1 and the ¾ Tdelay is 0 so XOR 190 outputs a 1. The falling edge of RS causesflip-flip 198 to output as Q2 what is at its D input, which is a 1. Q1continues to be 1. Accordingly, the output of AND gate 202 continues tobe a 1 even though there was a transition of RS.

At time t4, when RS has a rising edge, the ¼ T delay is 0 and ¾ T delayis 1 so XOR 190 outputs a 1. The rising edge of RS causes flip-flip 196to output as Q1 what is at its D input, which is a 1. Q2 continues tobe 1. Accordingly, the output of AND gate 202 continues to be a 1.

At time t4.5, RS does not transition. Accordingly, Q1 and Q2 do notchange and the data out signal does not change.

At time t5, when RS has a falling edge, the ¼ T delay is 1 and the ¾ Tdelay is 1 so XOR 190 outputs a 0. The falling edge of RS causesflip-flip 198 to output as Q2 what is at its D input, which is a 0. Q1continues to be 1. Accordingly, the output of AND gate 202 changes to a0.

At time t5.5, when RS has a rising edge, the ¼ T delay is 0 and ¾ Tdelay is 1 so XOR 190 outputs a 1. The rising edge of RS causesflip-flip 196 to output as Q1 what is at its D input, which is a 1. Q2continues to be 0. Accordingly, the output of AND gate 202 continues tobe a 0 even though there was a transition of RS.

At time t6, when RS has a falling edge, the ¼ T delay is 1 and the ¾ Tdelay is 0 so XOR 190 outputs a 1. The falling edge of RS causesflip-flip 198 to output as Q2 what is at its D input, which is a 1. Q1continues to be 1. Accordingly, the output of AND gate 202 changes to a1.

As can be seen, the value of the data out signal follows the value ofthe CES and CCES signals with a delay as described. As mentioned, withdifferent logic the data out signal could have the opposite value.Further, the receiver could use the data out* signal (which is theinverse of the data out signal) in place of the data out signal, ifdesired.

In summary, for the receiver of FIG. 4, the output of initial receivingcircuit 182 is delayed such that a sample is taken of the receivedsignal in each of two halves of the data time segment. In the case ofFIG. 4, the delays are by amounts of ¼ and ¾, but in other embodiments,delays by other amounts could be made. Further, in other embodiments,more than two delays may be made.

3. Synchronizing Circuits of FIGS. 8-9.

In some embodiments, additional circuitry is provided to synchronize thedata out and data out* signals to a periodic signal (for example, aclock or strobe signal) for use in other parts of chip or portion ofchip 16. For example, FIG. 8 illustrates a synchronizing circuit 200which synchronizes the data out and data out* signals between a firstperiodic signal (periodic signal 1) derived indirectly from the CES andCCES and a second periodic signal (periodic signal 2) used by otherportions of chip or portion of chip 16. Of course, the inventions arenot limited to the details of FIG. 8. When synchronizing circuit 200 isused in connection with receiver 180, the data out and data out* signalsare those from AND gates 202 and 204 and the 1 T delay signal is fromdelay circuit 184 of FIG. 4. A periodic signal deriving circuit 206provides periodic signal 1 to a first queue (queue 208) or a secondqueue (queue 210).

Queue 208 and queue 210 work in tandem so that when queue 208 is takingin the data out and data out* signals, queue 210 is providing outpreviously taken in data out and data out* signals for use by othercircuits (not shown). Likewise, when queue 210 is taking in the data outand data out* signals, queue 208 is providing out previously taken indata out and data out* signals. Periodic signal 1 is used to take in thedata out and data out* signals into queue 208 or queue 210 (for example,from AND gates 202 and 204 in FIG. 4). Periodic signal 2 is used toprovide out the previous stored data out and data out* signals fromqueue 208 or queue 210. Arbiter 216 determines whether periodic signals1 and 2 are applied to queues 208 and 210, respectively, or to queues210 and 208, respectively. There are various ways of implementingarbiter 216. One way is to include a counter that counts the number ofcycles or half cycles of periodic signal 1 and switch between queues 208and 210 after a certain number of cycles or half cycles are received.

The data out and data out* signals being output from queues 208 and 210may be serial or parallel signals. That is, queues 208 and 210 mayreceive serial data out and data out* signals and provide serial dataout and data out* signals. Alternatively, queues 208 and 210 may receiveserial data out and data out* signals and convert them to parallel dataout and data out* signals.

Periodic signal 1 may be an approximate square wave. Under one approach,the data out and data out* signals are inputted into queue 208 or 210 onboth edges of periodic signal 1. Under another approach, the data outand data out* signals are inputted on only the rising edge or on onlythe falling edge of periodic signal 1. Under still another approach,periodic signal 1 is made of two sub-signals that are 180 degrees out ofphase with each other. In this case, the data out and data out* signalscould then be inputted on the rising edge of both sub-signals, thefalling edge of both signals, or both rising and falling edges dependingon the implementations. Under other implementations, the data out anddata out* signals are inputted based on voltage levels rather thanedges. Periodic signal 2 may have the same frequency as periodic signal1 or may have a different frequency (e.g., a multiple of periodic signal1), depending on the implementation. However, in most cases, it isexpected that periodic signals 1 and 2 would be out of phase with eachother. As an example, periodic signal 2 may be a clock signal used inother parts of chip or portion of chip 16.

There are various ways in which periodic signal deriving circuit 206 canderive the periodic signal. In the illustrated embodiments of FIG. 8,periodic signal deriving circuit 206 uses the 1 T delay signal and thedata out and data out* signals, but various other signals could be used.

FIG. 9 illustrates one of the many possible implementations of periodicsignal deriving circuit 206. In FIG. 9, an AND gate 242 receives thedata out* signal and a signal fedback from OR gate 262. An AND gate 244receives the data out signal and a signal fedback from OR gate 264. XORgate 234 receives the 1 T delay signal and the signal fedback from ORgate 264. XOR gate 236 receives the 1 T delay signal and the signalfedback from OR gate 262. AND gate 254 receives the data out signal andthe output of XOR gate 234. AND gate 256 receives the data out* signaland the output of XOR gate 236. OR gate 262 receives the outputs of ANDgate 242 and 254. OR gate 264 receives the outputs of AND gate 244 and256. OR gate 264 outputs the periodic signal 1.

D. Receivers of FIGS. 10-11.

FIG. 10 shows other embodiments of receivers 28 and 104. Referring toFIG. 10, initial receiving circuit 318 (which may be the same as circuit182 in FIG. 4) receives CES and CCES and produces a received signal RSin response thereto. Delay circuit 320 provides a 1T delay signal, a ¼delay signal, and a ¾ delay signal. An XOR gate 332 provides a signal toflip-flops 336 and 338 in response to the ¼ and ¾ delay signals. A NORgate 326 provides a signal rising (SR) signal in response to an output(Q2) of flip-flop 338 and an inverted 1 T delay signal through inverter324. An OR gate 330 provides a signal falling (SF) signal in response toan output (Q1) of flip-flop 336 and the 1 T delay signal. A statemachine in the form of an AND gate 342 and an OR gate 344 provides anoutput control signal. AND gate 342 receives the SF signal and thefedback output control signal. OR gate 344 provides the output controlsignal in response to the output of AND gate 342 and the SR signal. MUXs352 and 354 are controlled by the output control signal. MUX 352receives the Q1 and Q2 signals and provides the data out signal. MUX 352receives inverted Q1 and Q2 signals (through inverters 346 and 348) andprovides the data out* signal. In some embodiments, there is only MUX352 or only MUX 354.

FIG. 11 is a timing diagram to illustrate the operation of the receiverof FIG. 10 for some embodiments. Other embodiments may have minor orsignificant deviations from that shown in FIGS. 10 and 11 and the followdescription. At or before time t0, flip-flops 336 and 338 are reset sothat Q1 and Q2 are 0 (low voltage). The values of SR and SF may bepredefined for the time before t1 so there are known values for the dataout and data out* signals.

At time t1, the 1 T delay signal is rising, and Q1 and Q2 are 0 so thatSR and SF both rise. Accordingly, flip-flop 336 passes the 0 output ofXOR 332 to Q1 and flip-flop 338 does not clock. Hence, Q1 and Q2 remain0. With SR being 1, the output control signal from OR gates 344 is 1.With SF 1, the output of AND gate 342 is 1. With the output controlsignal being 1, MUXs 352 and 354 pass Q1 and Q1*, respectively.

At time t1.5, the 1 T delay signal does not transition, so there is notchange in SF, SR, Q1, Q2, or the output control signal.

At time t2, the 1 T delay signal is falling, and Q1 and Q2 are 0 so thatSR and SF both fall. Accordingly, flip-flop 338 clocks the 0 output byXOR 332 to Q2 and flip-flop 336 does not clock. Hence, Q1 and Q2 remain0. With SF being 0, the output of AND gate 342 is 0. Further, since SRis 0, the output of OR gate 344 (output control signal) is 0. With theoutput control signal being 0, MUXs 352 and 354 pass Q2 and Q2*,respectively.

At time t2.5, the 1 T delay signal does not transition, so there is notchange in SF, SR, Q1, Q2, or the output control signal.

At time t3, the 1 T delay signal is rising, and Q1 and Q2 are 0 so thatSR and SF both rise. Accordingly, flip-flop 336 clocks the 1 output byXOR 332 to Q1 and flip-flop 338 does not clock. Hence, Q1 changes to 1and Q2 remains 0. With SR being 1, the output control signal from ORgate 344 is 1. With SF 1, the output of AND gate 342 is 1. With theoutput control signal being 1, MUXs 352 and 354 pass Q1 and Q1*,respectively.

At time t3.5, the 1 T delay signal is falling and Q2 is 0 so SR falls.However, Q1 is 1 which forces SF to remain 1 even though the 1 T delaysignal is falling. According, neither flip-flop 336 or 338 clocks dataand Q1 remains 1 and Q2 remains 0. As such, receiver 316 keeps theoutput control signal or data from changing during mid-segmenttransitions by blocking OR gate 330 from changing SF when Q1 is 1 andthe 1 T delay signal falls (as in the case of t3.5 and t4.5) or byblocking NOR gate 326 from changing SR when Q2 is 1 and the 1 T delaysignal rises (as in the case of t6.5). With SF being 1, the outputcontrol signal stays 1 and MUXs 352 and 354 continue to pass Q1 and Q1*,respectively. The output of AND gate 342 stays high.

At time t4, the 1T delay signal is rising and Q2 is 0 so SR rises andflip-flop 336 clocks the 1 output by XOR 332 to Q1. Q1 is 1 which forcesSF to remain 1. However, with 1 T delay rising, SF would be a 1 even ifQ1 were 0. Since SF remains 1, flip-flop 338 does not clock. With SRbeing 1, the output control signal stays 1 and MUXs 352 and 354 continueto pass Q1 and Q1 *, respectively. The output of AND gate 342 stayshigh.

At and following time t4.5, the signals are the same as at and followingtime t3.5.

At time t5, the 1 T delay signal is rising and Q2 is 0 so that SR rises.Accordingly, flip-flop 336 passes the 0 output of XOR 332 to Q1. Withthe 1 T delay signal rising, SF remains 1 and Q2 remains 0. With SRbeing 1, the output control signal from OR gate 344 is 1 and MUXs 352and 354 pass Q1 and Q1*, respectively. The output of AND gate 342 stayshigh.

At time t5.5, the 1 T delay signal does not transition, so there is notchange in SF, SR, Q1, Q2, or the output control signal.

At time t6, the 1 T delay signal is falling, and Q1 and Q2 are 0 so thatSR and SF both fall. Accordingly, flip-flop 338 clocks the 1 output byXOR 332 to Q2 and flip-flop 336 does not clock. Hence, Q2 changes to 1and Q1 remains 0. With SF being 0, the output of AND gate 342 is 0.Further, since SR is 0, the output of OR gate 344 (output controlsignal) is 0. With the output control signal being 0, MUXs 352 and 354pass Q2 and Q2*, respectively.

At time t6.5, the 1 T delay signal is rising and Q2 is 1 so that SRstays 0. As mentioned, this blocks flip-flop 336 from clocking. Since Q1is 0 and the 1 T delay signal is 1, SF changes to 1 and flip-flop 338does not clock. Therefore, Q1 and Q2 remain 0 and 1, respectively. Sincethe output control signal was 0 and SR is 0, the output control signalremains 0 even though SF is 1. Accordingly, MUXs 352 and 354 continue topass Q2 and Q2*, respectively.

At time t7, the 1 T delay signal is falling and Q1 is 0 so SF isfalling. SR is also 0. Accordingly, flip-flop 338 clocks the 0 output byXOR 332 to Q2 and flip-flop 336 does not clock. Hence, Q2 changes to 0and Q1 remains 0. With SF being 0, the output of AND gate 342 is 0.Further, since SR is 0, the output control signal is 0. With the outputcontrol signal being 0, MUXs 352 and 354 pass Q2 and Q2*, respectively.

The values of the data out signal are shown adjacent to the outputcontrol signal in FIG. 11. As can be seen, the output control signal hasthe same value as the CES and CCES with a delay of slightly more than 1data time segment. Of curse, different logic could be used so that thedata out signal has the opposite value as the CES and CCES.

In summary, the output control signal selects Q1 in response to SRrising shortly after the beginning of data time segment and selects Q2in response to SF falling shortly after the beginning of data timesegments. Receiver 316 blocks the effect of mid-segment transitions ofCES and CCES that otherwise would change the selection between Q1 and Q2or the output control signal.

Synchronizing circuit 200 in FIG. 8 may be used in connection withreceiver 316.

E. Additional Embodiments and Information

The inventions are not limited to use with complementary signals CES andCCES. For example, FIG. 12 shows a transmitter 384 (which is an exampleof transmitter 20 of FIG. 1) with cycle encoding circuit 152, but notcomplementary cycle encoding circuit 154 so that the CES but not theCCES is produced. Receiver 388 (which is an example of receiver 28 inFIG. 1) includes an initial receiving circuit 392, which may be acomparator, and which compares the CES to a reference signal Vref. As anexample, Vref might be between a high and low voltage for the CES. Toshow different possibilities, in FIG. 12, a DLL 382 provides a periodicreference signal rather than a PLL as in FIG. 4.

The inventions are not limited to use with only a 0 or 1 beingrepresented. For example, FIG. 13 illustrates a CES that can represent0, 1, or 2. The choice of which encoding signal SF, SF*, SF/2, SF/2*,SF/4, and SF/4* that represents 0, 1, and 2 is arbitrary. The signals ofFIG. 13 can be created by adding additional circuits to those ofcircuits 162-168 and 172-178. A receiver could take samples atadditional locations through for example, additional delays. Also, thelogic would be more complicated logic than shown in FIGS. 4 or 10. Morecircuits could be added to provide SF/8 and SF/8* to represent 0, 1, 2,and 3. The encoding signals do not have to be at divisions of two of themaximum frequency. For example, in some embodiments, the encodingsignals might include those with ⅔ or ¾ of the maximum frequency.

Another way to encode additional represented values (e.g., 0, 1, 2, 3)is to have additional voltage levels, rather than merely high or low.For example, the signals of FIG. 5 and 13 could have additional voltagelevels.

A partial CES includes some encoding signals with a period that is lessthan (for example, half) the data time segment while other encodingsignals have a period that is equal to or greater than the data timesegment. One way to accomplish this is to have the frequency of the PRSFof FIG. 4 be twice the frequency it is in FIG. 4 and to reduce thefrequency of it in creating only some encoding signals. The circuits ofan accompanying receiver would be such as to recover the input data froma CES and CCES with these frequencies.

In the CES's described in connection with FIGS. 4, 5, 7, 10, 11, 12, and13, there is only one encoding signal per data time segment. In otherembodiments, one encoding signal may be used in part of a data timesegment, while another encoding signal may be used in the remainder ofthe data time segment. Having more than one encoding signal in a datatime segment can be used to represent merely a 0 or 1 or to representmore than two values.

In the CES's described in connection with FIGS. 4, 5, 7, 10, 11, 12, and13, the data time segment is constant. In other embodiments, the datatime segment could have a variable width. Merely a 0 or 1 or more valuescould be thereby represented.

The inventions are not limited to a particular type of interconnectbetween the transmitter and receiver. For example, the illustratedversions of the transmitters and receivers show the interconnects asbeing electrical conductors that carry conventional electrical signals.However, various other types of interconnects could be used includingelectromagnetic interconnects (for example, wave guides (including fiberoptics) and radio-frequency (RF)). Merely as an example, FIG. 14illustrates an electromagnetic (EM) transmitter 450 in a transmitter 440that provides an EM signal on a wave guide 458 to EM receiver 452 in areceiver 444. As shown in FIG. 14, the CES is transmitted over the waveguide. There could also be such a EM transmitter and receiver coupledthrough a wave guide for the CCES.

FIG. 15 illustrates a system similar to that of FIG. 14 except that EMtransmitter 476 in transmitter 470 is a wireless transmitter and EMreceiver 478 in receiver 474 is a wireless receiver. As an example, theEM signal may be a radio frequency (RF) signal or another type of EMsignal. As an example, transmitter 476 and receiver 478 may include λ/4antennas.

Conductors 24A and 24B are not necessarily continuous but could includeintermediate circuits, vias etc. The conductors may include capacitorsfor serial AC coupling although that may slow the switching speed. Theinventions may be used in point-to-point interconnect systems as shownin FIGS. 1 and 2 in which there is one receiver for each transmitter.The inventions could also be used in a system in which a signal istransmitted from one transmitter to multiple receivers. The illustratedcircuits may include additional circuits such as electro-staticdischarge (ESD) circuits, enable signal control circuits, and timingchains. In alternative embodiments, the CES could be carrieddifferentially on two conductors and CCES could be carrieddifferentially on two conductors. Edge triggered circuits may bereplaced with level triggered circuits. Voltage controlled or currentcontrolled circuits could be used.

The term “responsive” means that one thing or event at least partiallycauses another thing or event, although there may be other causes forthe thing or event. Two circuits may be coupled directly or coupledindirectly through an intermediate circuit.

An embodiment is an implementation or example of the inventions.Reference in the specification to “an embodiment,” “one embodiment,”“some embodiments,” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments, of the inventions. The various appearances“an embodiment,” “one embodiment,” or “some embodiments” are notnecessarily all referring to the same embodiments.

If the specification states a chip, feature, structure, orcharacteristic “may”, “might”, or “could” be included, that particularchip, feature, structure, or characteristic is not required to beincluded. If the specification or claim refers to “a” or “an” element,that does not mean there is only one of the element. If thespecification or claims refer to “an additional” element, that does notpreclude there being more than one of the additional element.

The inventions are not restricted to the particular details listedherein. Indeed, those skilled in the art having the benefit of thisdisclosure will appreciate that many other variations from the foregoingdescription and drawings may be made within the scope of the presentinventions. Accordingly, it is the following claims including anyamendments thereto that define the scope of the inventions.

1. A chip comprising: a receiver to receive a full cycle encoded signalin which data is represented in data time segments and no data timesegment has more than one cycle, and provides a data output signalresponsive to the full cycle encoding signal, wherein the receiver is tofurther receive a complementary full cycle encoded signal and whereinthe receiver provides the data output signal responsive to the fullcycle encoded signal and the complementary full cycle encoded signal,further comprising a synchronizing circuit to synchronize the dataoutput signal to a second periodic signal and wherein the synchronizingcircuit includes a periodic signal deriving circuit to provide a firstperiodic signal in response to the full cycle encoded signal and whereinthe first periodic signal is used in the synchronizing.
 2. The chip ofclaim 1, wherein within some of the data time segments the full cycleencoded signal is the inverse of the cycle encoded signal within othersof the data time segments, and wherein within some of the data timesegments the full cycle encoded signal constitutes one cycle and withinothers of the data time segments the full cycle encoded signalconstitutes a half cycle.
 3. The chip of claim 1, wherein the receiverincludes an initial receiving circuit to compare the full cycle encodedsignal and the complementary full cycle encoded signal to provide areceived signal in response thereto, and the receiver includes a delaycircuit to provide at least two delayed signals which are delayedversions of the received signal, and a logic circuit to provide the dataoutput signal responsive to the delayed signals.
 4. The chip of claim 3,wherein the logic circuit also provides an inverse data output signal.5. The chip of claim 3, wherein the logic circuit responds to changesthe received signal at the beginning of a data time segment, but not tomid-data time segment changes in the received signal.
 6. The chip ofclaim 3, wherein the at least two delay signals include a ¼ data timesegment delay signal and a ¾ data time segment delay signal.
 7. The chipof claim 3, wherein the logic circuit includes an exclusive-OR gate toreceive the at least two delayed signals and the logic circuit includesfirst and second flip-flips to receive an output of the exclusive-ORgate and to receive the received signal at clock inputs of the first andsecond flip-flops, wherein the first flip-flop is clock on a rising edgeand the second flip-flop is clocked on a falling edge.
 8. The chip ofclaim 3, wherein the logic circuit includes an AND gate that receivesoutputs of first and second flip-flops and the data output signal is anoutput of the AND gate.
 9. The chip of claim 3, wherein the logiccircuit includes a state machine that provides an output control signalto control at least one multiplexer circuit to control whether the dataoutput signal is from a first flip-flop or a second flip-flop.
 10. Thechip of claim 1, wherein the receiver includes an initial receivingcircuit to compare the full cycle encoded signal and a reference signalto provide a received signal in response thereto, and the receiverincludes a delay circuit to provide at least two delayed signals whichare delayed versions of the received signal, and a logic circuit toprovide the data output signal responsive to the delayed signals. 11.The chip of claim 10, wherein the at least two delay signals include a ¼data time segment delay signal and a ¾ data time segment delay signal.12. A chip comprising: a receiver to receive a cycle encoded signal inwhich data is represented in data time segments and at least some datatime segments do not have more than one cycle, and to provide a dataoutput signal responsive to the cycle encoded signal; and asynchronizing circuit to synchronize the data output signal to a secondperiodic signal and wherein the synchronizing circuit includes aperiodic signal deriving circuit to provide a first periodic signal inresponse to the cycle encoded signal and wherein the first periodicsignal is used in the synchronizing.
 13. The chip of claim 12, whereinthe cycle encoded signal is a full cycle encoded signal in which no datatime segment has more than one cycle of an encoding signal.
 14. The chipof claim 13, wherein within some of the data time segments the fullcycle encoded signal is the inverse of the cycle encoded signal withinothers of the data time segments, and wherein within some of the datatime segments the full cycle encoded signal constitutes one cycle andwithin others of the data time segments the full cycle encoded signalconstitutes a half cycle.
 15. The chip of claim 12, wherein the receiverincludes an initial receiving circuit to receive the cycle encodedsignal and provide a received signal in response thereto, a delaycircuit to provide delayed signals which are delayed versions of thereceived signal and a logic circuit to provide the data out signalresponsive to the delayed signals which includes recovered data from thecycle encoded signal.
 16. The chip of claim 15, wherein the logiccircuit also provides an inverse of the data output signal.
 17. The chipof claim 15, wherein the logic circuit responds to changes the receivedsignal at the beginning of a data time segment, but not to mid-data timesegment changes in the received signal.
 18. The chip of claim 15,wherein the logic circuit includes an AND gate that receives outputs offirst and second flip-flops and the data output signal is an output ofthe AND gate.
 19. The chip of claim 15, wherein the logic circuitincludes a state machine that provides an output control signal tocontrol at least one multiplexer circuit to control whether the dataoutput signal is from a first flip-flop or a second flip-flop.
 20. Thechip of claim 12, wherein the receiver further receive a complementarycycle encoded signal and wherein the receiver provides the data outputsignal responsive to the cycle encoded signal and the complementarycycle encoded signal.
 21. The chip of claim 20, wherein the receiverincludes an initial receiving circuit to compare the cycle encodedsignal and the complementary cycle encoded signal to provide a receivedsignal in response thereto, and the receiver includes a delay circuit toprovide at least two delayed signals which are delayed versions of thereceived signal, and a logic circuit to provide the data output signalresponsive to the delayed signals.
 22. The chip of claim 21, wherein thelogic circuit responds to changes the received signal at the beginningof a data time segment, but not to mid-data time segment changes in thereceived signal.
 23. The chip of claim 21, wherein the logic circuitincludes an exclusive-OR gate to receive the at least two delayedsignals and the logic circuit includes first and second flip-flips toreceive an output of the exclusive-OR gate and to receive the receivedsignal at clock inputs of the first and second flip-flops, wherein thefirst flip-flop is clock on a rising edge and the second flip-flop isclocked on a falling edge.
 24. The chip of claim 12, wherein within someof the data time segments the cycle encoded signal is at the samevoltage at a beginning and an end of the data time segments, and whereinwithin some of the data time segments the cycle encoded is at the samevoltage at a beginning, middle, and end of the data time segments, andwherein within some of the data time segments the cycle encoded signalis an inverse of the cycle encoded signal within others of the data timesegments.
 25. A system comprising: a transmitter including: (a) a cycleencoding circuit to receive a data input signal and to provide a cycleencoded signal in response thereto by continuously joining portions ofdifferent encoding signals, wherein some of the encoding signals have adifferent frequency than others of the encoding signals and some of theencoding signals have a different phase than others of the encodingsignals; and (b) a complementary cycle encoding circuit to receive thedata input signal and to provide a complementary cycle encoded signal inresponse thereto by continuously joining portions of the differentencoding signals; and a receiver to receive the cycle encoded signal andthe complementary cycle encoded signal and to recover values of the datainput signal in response thereto to provide a data output signal,wherein the receiver includes an initial receiving circuit to comparethe cycle encoded signal and the complementary cycle encoded signal toprovide a received signal in response thereto, and the receiver includesa delay circuit to provide at least two delayed signals which aredelayed versions of the received signal, and a logic circuit to providethe data output signal which represents the recovered values, whereinthe logic circuit provides the data output signal responsive to thedelayed signals, wherein the logic circuit includes an exclusive-OR gateto receive the at least two delayed signals and the logic circuitincludes first and second flip-flips to receive an output of theexclusive-OR gate and to receive the received signal at clock inputs ofthe first and second flip-flops, wherein the first flip-flop is clock ona rising edge and the second flip-flop is clocked on a falling edge. 26.The system of claim 25, wherein the encoding signals include a firstsignal with frequency F, a second signal that is an inverse of the firstsignal, a third signal that has a frequency F/2, and a fourth signalthat is an inverse of the third signal.
 27. The system of claim 25,wherein the cycle encoded signal is a full cycle encoded signal and thecomplementary cycle encoded signal is a complementary full cycle encodedsignal in which no data time segment has more than one cycle of anencoding signal.
 28. The system of claim 25, wherein the logic circuitresponds to changes the received signal at the beginning of a data timesegment, but not to mid-data time segment changes in the receivedsignal.
 29. The system of claim 25, further comprising a synchronizingcircuit to synchronize the data output signal to a second periodicsignal and wherein the synchronizing circuit includes a periodic signalderiving circuit to provide a first periodic signal in response to thecycle encoded signal and wherein the first periodic signal is used inthe synchronizing.